This invention relates to marking pens and more particularly to marking pens having a free liquid ink reservoir.
Marking pens are well-known and comprise an elongate applicator made of fibres or other suitable material that is rounded or otherwise shaped and at one end formed a marking face. The applicator is supported in and arranged to be exposed out of one end of a hollow shank. The other end of the applicator is supplied with ink as required. Commonly an ink supply is held in a porous pad that is retained inside the shank. Small air vent passages are provided around the applicator to allow air to pass into the shank so that ink will flow more satisfactorily from the absorbent pad into the applicator. Such arrangement of an absorbent pad reservoir is less prone to cause leakage than the use of a free liquid ink reservoir.
It is sometimes desired to have a free liquid ink reservoir in preference to an absorbent pad reservoir for various reasons; for example, it would be difficult to replenish the ink supply held in a pad or have a convenient adequate ink supply for any purposes. It has already been proposed to use a liquid ink reservoir and to provide xe2x80x9cmechanicalxe2x80x9d valves that are automatically activated by actual use of the pen, that is when the applicator is arranged to be slidingly depressed into the shank, so that the liquid ink is retained at other times in a secondary smaller reservoir inside the shank. Such mechanical valves are disclosed in Japan Patent Specification 11334278 and U.S. Pat. No. 3,640,631, for example. Other xe2x80x9cmechanicalxe2x80x9d means for controlling the liquid ink flow or delivery and/or any possible leakage have also been proposed, one as in United Kingdom Patent Specification 2170697. There are inherent problems in using xe2x80x9cmovingxe2x80x9d mechanical parts especially in association with volatile liquids, such as inks, due to contamination of the valve parts. Also, the mechanical valve parts require comparatively close manufacturing and assembly tolerances for satisfactory or reliable operation.
It is an object of the invention to overcome or at least reduce some of these problems.
According to one aspect of the invention, there is provided a marking pen having a liquid ink reservoir for containing a liquid ink and a liquid ink applicator for delivering the liquid ink from the reservoir to a marking face of the applicator in which the reservoir has an opening comprising a channel as an outlet for the liquid ink and a portion of the applicator is fittingly and fixedly disposed in the channel and co-operatively working with the channel substantially sealing the opening such that the liquid ink substantially flows out of the reservoir via the applicator.
In practice, the channel is preferably formed by a sealing means seated at the opening of the reservoir. The sealing material of the sealing means would work more efficiently with the absorbent material of the applicator in sealing the opening of the reservoir.
In accordance with a further aspect of the invention, stopping means made of material more absorbent than that of the applicator may also be provided surrounding at least an intermediate portion of the applicator.
According to another aspect of the invention, there is provided a marking pen having an elongate hollow shank with an open end, a liquid ink reservoir inside and adjacent a closed end of the shank, an applicator supported in the open end of the shank with a remote end of the applicator partially exposed out of the shank, and small aperture vent passage means extending from adjacent the remote end to a buffer zone cavity inside the shank adjacent an intermediate part of the applicator and sealed off from the reservoir such that the passage means allow air to pass into or out of the buffer zone to maintain atmospheric pressure therein. The buffer zone is preferably at least partially filled with porous material.
The applicator may comprise two end-to-end parts preferably of substantially the same length and one part conveniently extends into the reservoir through a channel, which can be formed by a seal, and may therefore be sealingly connected to the liquid ink reservoir in the shank. To achieve a more satisfactory flow of the liquid ink, the one part of the applicator may preferably have a higher porosity than the other part of the applicator.
The buffer zone preferably completely surrounds the one part of the applicator and is further filled with material that is more porous than that of the one part. The porous material in the buffer zone may comprise a strand of material wound in a spiral around the one part, and extend to lie against inner ends of the passage means.